I mentioned something about a demonstration setup in the www.jpaerospace.com thread and I keep wondering if a two stage ATO is possible. Seems to me that it ought to be possible and in some ways may have an advantage over the three step ATO concept. I think the three step idea with the dark sky station is probably the best bet for setting up a robust cargo infrastructure. I just keep thinking that if a two stage ATO is possible it may be the best way to prove the concept and do so at a relatively low cost.

as far as I remember jpowell has explicitly said elsewhere that the ATO itself - the vehicle launching from the Dark Sky Station into an orbit - will have to be built at the Dark Sky Station at 42 km altitude and couldn't go there - 42 km or orbit - from ground.

To me this sounds as if there is no way out of the three stage concept and he is bound to it even to prove the concept.

I was thinking about the possibility of building an Ascender type craft that was large enough to carry a completed ATO stage and then launching that ATO from the Ascender. That would bypass the additional work of building a Dark Sky Station and assembling an ATO at the station.

A big inflatable--wider than anything bigelow has looked at--would be a nice work area on the moon. With a floor a dome--all surrounding a metal tube (lock-out) in the center where the lunar surface is exposed for work--perhaps drilling into a cave below. An Airship might be a good template.

A two stage ATO is much harder. It may not be doable. The final stage airship is a order of magnitude bigger the the first stage airship.
It also could easily be destroyed by winds in the lower atmosphere.

The three stage system makes everything much more reasonable.

As for a quick demo of the technology we fly a piece of ATO on every mission we fly, 89 so far. There are about 40 more to go. There's a lot of tech to develop. The step by step approach has worked for us very well so far.
A quick flashy demo of an ATO "looking" vehicle before we're ready would hurt the program in the long run. We've been at it for 28 years now. A few more to get it right it a good investment.